ZTEC Instruments

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ZTEC Instruments
Our Presentation will Start Shortly

• PXI Modular Oscilloscope Measurement Fundamentals
  
• Creston Kuenzi, Applications Engineer

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ZTEC Instruments

• PXI Modular Oscilloscope Measurement Fundamentals
  
• Creston Kuenzi, Applications Engineer

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Co-Host - PXISA

• Manage PXI System Alliance, Founded in 1998
• About 70 Member Companies, Worldwide, Evolve PXI
  Specifications
• Promote PXI

www.pxisa.org
Source Prime Data, 2003
info_at_pxisa.org
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Co Host - ZTEC

• Based in Albuquerque, New Mexico
• Manufacturer of innovative modular
  instrumentation products with a focus on PCI, PXI
  and VXI oscilloscopes
• Applications include military, aerospace,
  manufacturing, and scientific research
• Customers in over 25 Countries worldwide
• Celebrating 10th year anniversary in 2006
• The Leader in Modular Oscilloscopes

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Our Speaker Creston Kuenzi

• BS in Computer Engineering from Kansas State
  University 1999
• Applications Engineer and Field Sales Engineer
  for National Instruments 20002006
• Applications Engineer for ZTEC Instruments
  2006Present

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Purpose
Learn About PXI Modular Oscilloscope Measurement
Capabilities in Order to Avoid Inaccurate or
Misunderstood Results
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Agenda

• Introduction to PXI Modular Oscilloscopes
• Vertical-Axis Measurements
• Horizontal-Axis Measurements
• Frequency-Domain Measurements
• Conclusions

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Introduction to PXI Modular Oscilloscopes
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What is a Modular Oscilloscope?
Modular Oscilloscope
Modular Oscilloscopes Combine the Power of a
Benchtop Oscilloscope and the Flexibility of a
High-Speed Digitizer
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PXI Modular Oscilloscope Capabilities
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Oscilloscope Measurements
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Oscilloscope On-Board Measurement Variations

• All True Oscilloscopes Have On-Board Measurements
• These Measurements May Differ from Vendor to
  Vendor in Quantity, Name, and by the Algorithms
  Used
• Todays Discussion Will Show PXI ZTEC Scope
  On-Board Measurements
• Some of These Same Measurements are Found on
  Other Oscilloscopes.

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Categories of Onboard Measurements

• Vertical-Axis Measurements
• Horizontal-Axis Measurements
• Frequency-Domain Measurements

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Vertical-Axis Measurements
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Vertical-Axis Measurements

• Analyze the vertical component of the applied
  signal
• Most often describe a signal in terms of a
  voltage level
• Can also correspond to current, power, or any
  other physical phenomena converted to voltage via
  a probe or transducer

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Common Vertical Measurements

• Amplitude
• Peak To Peak
• Overshoot
• Undershoot
• Maximum
• Minimum
• Average
• RMS
• Etc

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Common Vertical Measurements
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Vertical-Axis Measurement Demo
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AC RMS, DC RMS, Average

• Average
• Mean Value of Waveform
• DC RMS
• Direct Current (DC) Root Mean Square (RMS)
• DC RMS v(?V2) / Number of points
• Average Power of Signal
• AC RMS
• Alternating Current (AC) Root Mean Square (RMS)
• AC RMS v(?(V-Vavg)2) / Number of points
• Average Power of Signal Excluding DC Offset

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AC RMS, DC RMS, Average
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AC RMS, DC RMS, Average

• Partial Cycles Can Return Inaccurate Measurements

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Avoiding Partial Cycle Problem

• Acquire Longer Waveforms to Reduce Affect
• Use Cycle RMS and Cycle Average Measurements
• Use Gated Waveform Measurements

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AC RMS, DC RMS, Average Demo
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Histogram Processing vs Waveform Processing

• Histogram Processing
• Generates a Histogram of the Voltage Values and
  Looks for a Single Characteristic
• Very Fast Measurements but Less Accurate
• Examples Amplitude and PTPeak Measurements
• Waveform Processing
• Uses an Algorithm on Every Waveform Sample
• More Accurate but Slower than Histogram
  Processing
• Examples Average, DC RMS, and AC RMS
  Measurements

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Histogram Processing vs Waveform Processing

• Histogram of Voltage Values in an 8-bit
  Oscilloscope

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DC Power Supply Example
Transient Signal Generated from DC Power Supply
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Horizontal-Axis Measurements
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Horizontal-Axis Measurements

• Analyze the horizontal time axis of the applied
  signal
• Usually describe the signal in terms of time
• May also return a value expressed as a ratio,
  radians, or in Hertz

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Common Horizontal Measurements

• Waveform Measurements
• Period
• Frequency
• Edge Measurements
• Crossing Time
• Rise Time
• Fall Time

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Common Horizontal Measurements
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Common Horizontal Edge Measurements
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Demo of Horizontal Measurements
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Noise Issue on Vertical Axis Causes Edge Problems

• Vertical Noise Can Affect Horizontal Measurements

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Demo of Vertical Noise Causing Horizontal
Measurement Error
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Telecommunications T1 Example
T1 Signal Mask of Horizontal Measurements
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Frequency-Domain Measurements
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Frequency-Domain Measurements

• Translate a time-domain waveform with a fast
  Fourier transform (FFT), and then measure the
  noise and distortion characteristics in the
  frequency domain.
• Provide magnitude and phase characteristics
  versus frequency.
• Reveal signal characteristics that cannot be seen
  within the time-domain.

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Fast Fourier Transform (FFT)
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FFT Windows

• Used to increase spectral resolution in the
  frequency-domain.
• The Rectangular Window provides the best
  frequency and worst magnitude resolution. It is
  almost the same as no window.
• The Blackman-Harris Window provides the best
  magnitude and worst frequency resolution.
• The Hamming Window provides better frequency and
  worse magnitude resolution than the Rectangular
  Window. It provides slightly better frequency
  resolution than the Hanning Window.
• The Hanning Window provides better frequency and
  worse magnitude resolution than the Blackman
  Window. It provides slightly better magnitude
  frequency than the Hamming Window

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Demo of FFTs and Windows
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Common Frequency-Domain Measurements

• Signal-to-Noise Ratio (SNR) is the ratio of the
  RMS amplitude of the fundamental frequency to the
  RMS amplitude of all non-harmonic noise sources.
• Total Harmonic Distortion (THD) is the ratio of
  the RMS amplitude of the sum of the first nine
  harmonics to the RMS amplitude of the
  fundamental.
• Spurious-Free Dynamic Range (SFDR) is the ratio
  of the RMS amplitude of the fundamental to the
  RMS amplitude of the largest spurious signal.
• Signal-to-Noise and Distortion (SINAD) is the
  ratio of the RMS amplitude of the fundamental to
  the RMS amplitude of the sum of all noise and
  distortion sources.
• Effective Number of Bits (ENOB) is another way of
  expressing SINAD. It provides a measure of the
  input signal dynamic range as if the signal were
  converted using an ideal ADC.

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Demo of Frequency-Domain Measurements
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High-Speed ADC Test Example
FFT of ADC Two-Tone Distortion Test
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Summary

• PXI Modular Oscilloscopes Have Powerful Onboard
  Measurements
• The Three Categories on Measurements are
  Vertical-Axis, Horizontal-Axis, and Frequency
  Domain
• Understanding These Measurements Will Help You
  Improve Your Tests and Avoid Problems

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Questions?
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Thank you!

• ZTEC Instruments
• www.ztecinstruments.com
• ZTEC Instruments
• 7715 Tiburon St. NE
• Albuquerque, NM 87109
• Phone [phone]
• Fax [phone]
• isupport_at_ztec-inc.com
• PXI Systems Alliance
• www.pxisa.org
• 361 2nd Avenue, Suite 203
• PO Box 1016
• Niwot, Colorado 80544-1016
• Phone [phone]
• Fax [phone]
• Info_at_pxisa.org